This invention relates to an antenna for transmitting and/or receiving electro-magnetic radiation, from the infrared and visible range of wavelengths to the radar and microwave wavelengths. For purposes of this application the term optical radiation will be used to refer to the electro-magnetic radiation in the visible and infrared spectrum while the terminology high frequency electro-magnetic radiation will be used to identify radiation in the range of centimeter or millimeter wavelengths, such as radar and microwaves. These antennas may be used in the military field.
Modern, well equipped armies increasingly need to provide their armoured vehicles and other battle participants with devices for receiving and/or transmitting laser radiation, particularly in the infrared range, as well as radar radiation. Devices for laser and radar warning, e.g. warning of incoming airplanes which make use of radar fire control, or warning of battle field surveillance radar, are practically indispensable. Fire control radar for artillery must also be able to be detected, preferably with detection of the arrival direction, in order to gain reaction time when a risk is in the offing. Facility for detection as well as emission of infrared types of signal is likewise necessary because infrared fire searchlights, laser target illuminators, laser range-finders, and laser interrogation signals for friend/foe recognition (IFF) are used on the battlefield. Laser transmission paths for communication and laser weapon simulators used for the purposes of practice and training are also desirable.
Communication between units which may move freely and independently in the battlefield is important. The hopeless overcrowding of the militarily usable wireless frequency signals demands escape solutions for direct communication on the battlefield. Therefore increased utilization of radar and laser frequency bands for short communication paths with free optical sight is necessary. For this purpose, microwave signals in the centimeter and millimeter range, as well as laser signals of wave lengths from 0.9 to approximately 2 microns (.mu.) for example are of interest. Furthermore, for reasons of energy, as well as for avoiding the risk of interception, it is advantageous in many cases to be able to directionally transmit and receive in each sector.
Heretofore, transmitting and receiving devices for optical signals and for radar signals have been constructed fundamentally separate from each other. This has disadvantages because of space requirements, and because of the difficulty of finding suitable locations for attachment of the equipment. For example, on an armoured vehicle, the difficulty in locating the transmitting and receiving devices arises because of the need to protect the devices as much as possible from damage and yet to place them so that the emission and/or reception of signals in largely unimpeded. When the transmitting and/or receiving device must additionally have a directional characteristic or with a freely selectable transmission and/or reception direction, the realization of a usable device with the means known heretofore is even more difficult. For example, the rotatable parabolic antennas known in the art and used for radar reception are too heavy, too expensive and too sensitive for military use. Moreover, while such antennas admittedly have a directional characteristic, they must be swung or continuously rotated for the reception of signals coming from any desired direction and for the reply thereto in the same direction. Furthermore, these antennas are unsuitable for the reception of modern pulse-coded signals, since the adjustment periods necessary for this purpose are longer by orders of magnitude than the duration of such signals.